To punch an angled hole in a sheet, generally, a die unit must be provided which enables a punch to slide at an angle with respect to the sheet. Such a device is disclosed in Japanese Unexamined Patent Publication No. 207600/1991. A die unit set forth in this publication can be used to make a press-formed object having first and second holes, whose diameters are equal and whose punch directions are symmetrical about a direction normal to the sheet. In this publication, the first hole is first press-formed. Then, the die unit is rotated about a direction normal to the sheet, and the second hole is press-formed.
However, when the die unit is rotated (moved) to form the second hole, the position of the die with respect to the sheet (the workpiece) shifts. It is therefore necessary to adjust the position of the die unit with respect to the sheet (this adjustment is hereinafter referred to as a positioning operation). This operation is carried out after the die unit is rotated (moved).
Consequently, when a die unit is rotated every time one hole is punched for manufacturing press-formed objects, at least one positioning operation occurs during the manufacture of each press-formed object. This increases manufacturing man-hours (manufacturing time). As a result, productivity is lowered, thus making it difficult to achieve manufacturing cost reductions. This especially impacts large volume manufacturing. The present invention was developed in light of these drawbacks.